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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Imported Fire Ant and Household Insects Research » Research » Publications at this Location » Publication #128151
Title: BEAUVERIA BASSIANA YEAST PHASE ON AGAR MEDIUM AND ITS PATHOGENICITY AGAINSTDIATRAEA SACCHARALIS (LEPIDOPTERA: CRAMBIDAE) AND TETRANYCHUS URTICAE (ACARI: TETRANYCHIDAE)

Author
item ALVES, SERGIO - BRAZIL
item ROSSI, LUCIANA - BRAZIL
item LOPES, ROGERIO - BRAZIL
item TAMAI, MARCO - BRAZIL
item Pereira, Roberto

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2002
Publication Date: 7/1/2003
Citation: ALVES, S.B., ROSSI, L.S., LOPES, R.B., TAMAI, M.A., PEREIRA, R.M. BEAUVERIA BASSIANA YEAST PHASE ON AGAR MEDIUM AND ITS PATHOGENICITY AGAINSTDIATRAEA SACCHARALIS (LEPIDOPTERA: CRAMBIDAE) AND TETRANYCHUS URTICAE (ACARI:TETRANYCHIDAE). JOURNAL OF INVERTEBRATE PATHOLOGY. 2003. v. 81. p. 70-77.

Interpretive Summary: The insect pathogen Beauveria bassiana causes diseases in several insects. This fungus grows as yeast-like cells inside insects and in liquid cultures. However, this type of growth has not been observed on solid or semisolid medium. Scientists at USDA-ARS, CMAVE, Gainesville, FL and the Dept. of Entomology, Phytopathology and Agricultural Zoology, ESAL/Univ. Of fSao Paulo, Piracicaba, SP, Brazil, describe the use of a solid agar medium to grow the yeast-like cell of B. bassiana, and the virulence of these cells against insect hosts. Yeast-like cells are as virulent as, and sometimes more virulent than conidia against insect hosts. The production of B. basssiana yeast-like cells on agar medium may be an important step in studies of the biology, nutrition, pathogenesis, and the genetic manipulation of these fungi. Also, the production of these cells on solid medium may open new opportunities for mass-production and formulation of this entomopathogen as bioinsecticide for use in agriculture and other applications.

Technical Abstract: Beauveria bassiana colonizes insect hosts initially through a yeast phase, which is common in some artificial liquid cultures, but not reported on artificial solid media. We describe a yeast-like phase for B. bassiana isolate 447 on MacConkey agar and its virulence toward Diatraea saccharalis and Tetranychus urticae. The yeast-like cells of B. bassiana developed by budding from germinating conidia after 24-h incubation. Cells were typically 5 to 10 um and fungal colonies were initially circular, with a mucoid aspect, but later were covered with mycelia and conidia. Ability to produce yeast-like cells on MacConkey medium was present in different B. bassiana isolates, but growth rate and timing of yeast-like cell production varied. M. anisopliae and Paecilomyces spp. isolates did not grow as yeast-like cells on MacConkey medium. Yeast-like cells were more virulent against D. saccharalis than conidia at 10^7 cells/ml rate. At 10^8 cells/ml, the LT50 was 5 d for the yeast and 9 d for the conidial suspension, perhaps due to faster germination. The LC50 was also lower for yeast than conidial suspensions. Yeast-like cells and conidia had similar virulence against T. urticae; the average mortalities were, respectively, 42.8 and 45.0%, with 10^7 cells/ml, and 77.8 and 74.4%, with 10^8 cells/ml. The LT50's were 3.4 and 4.0 d for yeast and conidial suspensions, respectively. The bioassay results demonstrate the yeast-like structures are effective as inoculum for B. bassiana applications against arthropods, and possibly superior to conidia. Obtaining well-defined yeast phase cultures of entomopathogenic hyphomycetes may be an important step in studies of the biology and nutrition, pathogenesis, and the genetic manipulation of these fungi.